Understanding the diverse biochemical and molecular processes of the heart has been limited by the lack of appropriate cell lines. In this application we propose to develop cardiocyte cell lines. Studies on the mechanism of cellular transformation suggest that activation of one or more oncogenes can be used to perpetuate cell growth and division and has proven to be useful method for cell immortalization. Further, recent advances in our analysis of the gene encoding the cardiac-specific peptide, atrial natriuretic factor (ANF), provide a new set of tools that permit activation of particular genes exclusively in the atria and ventricle. We propose to use these genetic tools to target oncogenes to cardiac myocytes. Specifically, we will construct hybrid genes bearing ANF regulatory sequences fused to oncogene sequences. These will be initially introduced into primary cultured cardiocytes derived from neonatal rats. Constructs which are appropriately expressed in primary cultures will be stably introduced into the mouse germline using a transgenic mouse system. Analyses of hearts and primary cultured cardiocytes derived from ANF- oncogene transgenic mice should provide insights into physiologic and pathologic myocardial growth and hypertrophy. Cardiac tissues derived from transgenic mice will be used to develop stable cell lines. These lines should be a valuable resource to investigate many aspects of myocardial cellular and molecular biology.